The present invention relates generally to a tool holder, and more particularly to a holder for tools and similar objects having a shank provided with a transverse groove. Still more particularly, the invention relates to a holder which is especially suitable for holding tools in a power tool, such as a drill or a power chisel.
Various types of tool holders to hold a tool bit to the housing of a power tool, are already known. Many of these employ the conventional jaw-type chuck. Another prior-art construction utilizes, in the context of a pneumatic hammer, a tool holder in which a plurality of spherical locking elements extend into associated recesses formed in the shank of a tool bit. A slidable sleeve can be moved to and from a position in which it prevents the displacement of the spherical locking elements out of the associated recesses, thus holding the tool bit in place. The shank of the tool bit is receivable in a holding tube and the sleeve surrounds this tube which is formed with appropriate cutouts through which these spherical elements can yield in radially outwardly direction unless they are prevented from so doing by the presence of the sleeve. A mounting ring is provided which prevents unintentional or undesired removal of the sleeve from the tube.
However, this last-described prior-art construction has disadvantages, not the least of which is the fact that the surface-to-surface contact between these spherical locking elements and the shank of the tool bit is very small so that high pressures must be transmitted between the contacting surfaces via these very small points of contact, which leads to very rapid and pronounced wear and/or strong deformation of the contacting surfaces. Moreover, this prior-art construction is quite complicated and therefore expensive to produce and difficult to maintain.